Ferrous ion transport by strict anaerobes and facultative anaerobic bacteria will be investigated. Our objective will be to seek evidence that ferrous ionophores, analogous to ferric ionophores in aerobic microorganisms, are procduced by these organisms as a means of solubilizing and transporting iron. The strict anaerobe, Desulfovibrio desulfuricans, will be examined because of its high iron requirements inspite of the fact that it grows in the presence of elevated concentrations of sulfide. Iron transport will be followed during exponential growth using Fe-59. Low molecular weight ferrous chelates will be sought in the culture supernatant and in cell-free extracts by organic extraction, chromatography and electrophoresis, and gel filtration. The chelates will be purified and their structures determined with particular reference to the nature of the iron binding center. Parallel experiments will be done with E. coli grown anaerobically. We will determine if anaerobic E. coli possesses the ferric enterobactic and ferrichrome transport systems that are used aerobically. We will examine the transition of this organisms with respect to its assimilation of iron in going from anaerobic to aerobic growth conditions. The kinetics of iron uptake via ferrous ionophores will be determined and compared to the aerobic systems, and the specificity of the transport system will be examined.